<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style>
			.div1 {
				background-color: #f00;
				height: calc(100vh - 200px);	
			}
		</style>
	</head>
	<body>
		<div class="div1"></div>
	</body>
</html>